Cotton Host Plant Resistance To Silverleaf Whitefly Is Discovered
Foreground: little whitefly damage to okra-leaf cotton. Background: whitefly damaged cotton varieties.
What Has ANR Done?Host plant resistance offered one possible alternative for whitefly control in cotton. UCCE test results showed significant differences among cotton varieties and breeding lines for whitefly infestation levels. Two resistance mechanisms were discovered, smooth leaf cotton and okra-leaf shape cotton.
Smooth leaf cotton supported fewer whiteflies than hairy leaf cotton. Leaf hairiness is associated with increased boundary layer humidity on leaf surfaces. Extremely high air temperatures, low relative humidity, and limited irrigation in the desert southwest may result in subtle changes in underleaf humidity influencing Bemisia egg and nymph survival.
Okra-leaf cotton had fewer whitefly adults, eggs and nymphs than normal-leaf cotton. The okra-leaf characteristic may provide higher ambient temperature and lower humidity in the cotton canopy, creating a micro-climate unfavorable to whitefly survival.
Whitefly-resistant cotton varieties reduce insecticide usageHost plant resistance to whiteflies is clearly offering an economical and non-polluting alternative to whitefly management in cotton. Planting of the cotton varieties DP 5415 and NuCotn 33B, which are less susceptible to infestation by silverleaf whitefly, contributed to a reduction in insecticide use on cotton in Southern California since the early l990s. FiberMax okra-leaf cotton varieties with some whitefly resistance are now being marketed in the US and California, giving growers an additional whitefly management option.
Supporting Unit:Imperial County
Eric T. Natwick, UC Cooperative Extension
UC Desert Research & Extension Center
1050 East Holton Road, Holtville, CA 92250-9615
760) 352-9474 (Voice) (760) 352-0846 (Fax)